Ferry receives US warship warning

A passenger ferry on the River Clyde was unwittingly caught up in an international war exercise.
http://news.bbc.co.uk/1/hi/scotland/...st/6079974.stm


All was well on this occasion, but, what if the position was reversed? Say for instance a British naval vessel had got involved say with the Staten Island Ferry? Might it have been explained away so easily?